OK, thanks. So I'll just run a CHKDSK /R on it.
I'll give it a try on my son's computer tomorrow. I am a bit concerned because Acronis stopped at the 3% mark. Hopefully that's past the bootable sectors - in fact I'm guessing that it has to be, otherwise I wouldn't have been able to boot in the first place! But I'm still keeping my fingers crossed here - like I said, flying without a parachute.
If everything goes well, I'm guessing you would suggest making a clone and replacing this HD. That would make sense to me.